1. Field of the Invention
This invention relates to the manufacture of catalyst particles. In one aspect, the invention relates to the manufacture of finished catalyst particles having a relatively low crush strength, e.g. less than 10 pounds, while in another aspect, the invention relates to the control of the change in the crush strength of the catalyst particles as the catalyst precursor is transformed into a finished catalyst by calcination.
2. Description of the Prior Art
Often times the activity of a catalyst particle, typically a tablet, is related to its crush strength, i.e. its resistance to breakage when subjected to some force. Generally, the higher the crush strength of a catalyst particle, the more tightly packed or dense the particle and thus the less porous the particle. Again, generally, the less porous the catalyst particle, the less active the catalyst particle. However, generally the more porous the catalyst particle, the more likely the catalyst particle will be eroded under reaction conditions and thus the more likely catalyst mass will be lost over time. Likewise, the lower the crush strength of a catalyst particle, the more likely it will break during handling or loading of a reactor This can be a particularly acute problem in continuous processes where catalyst errosion can result in the formation of catalyst fines that are carried from the reaction zone with the reaction effluent or in an increased back pressure in the reactor. As a consequence, catalyst particles are desirably manufactured with a crush strength that maximizes porosity but minimizes attrition. Unfortunately, this desirable manufacture is difficult to achieve on a consistent basis.
The crush strength of a catalyst precursor particle can generally be readily controlled by simply programming or adjusting the settings of the apparatus, e.g. a tabletting machine, used to shape the particle. However, one particular problem in achieving the desired manufacture mentioned above is that the crush strength of the catalyst particle undergoes change during the calcination step that is generally used to transform a catalyst precursor into a finished catalyst. This change has been subject to little control, e.g. the crush strength of finished catalyst particles may vary in the low crush range from batch to batch relatively independent of the apparatus setting used to form the catalyst precursor particles. As such, it is difficult, if not impossible, to consistently manufacture low crush strength, finished catalyst particles having approximately the same low crush strength.